Usher Syndrome: Type ID

Usher syndrome type I (USH1) is an inherited disorder that causes hearing loss at birth and progressive vision loss starting in adolescence. The vision loss begins as night blindness in early adolescence followed bya gradual loss of peripheral vision. Development of cataracts may further reduce vision. Children with USH1 also learn to sit and walk at a later age than other children and have balance problems as they grow older. The life expectancy and intellect of individuals with USH1 is not affected. Without help from a cochlear implant, individuals typically do not develop speech. USH1 is caused by pathogenic variants in several genes, including MYO1A, USH1C, CDH23, and PCDH15.

Usher syndrome type I is inherited in an autosomal recessive manner. This type of inheritance requires the presence of two copies of a pathogenic variant in the gene for a person to have the genetic disease. Both parents must be carriers of a pathogenic variant in the gene in order to be at risk to have an affected child. The child must inherit a pathogenic variant from each carrier parent in order to be affected. There is a 1 in 4 chance that a baby will inherit two mutated copies of the gene and be affected when both parents are carriers.

There are generally no signs or symptoms associated with being a carrier for USH1. However, the risk to have a child affected with USH1 is increased. Testing of reproductive partners is recommended for carriers of USH1.

Usher syndrome is estimated to occur in approximately 3 to 6 per 100,000 newborns in Northern Europe and at least 4 in 100,000 newborns in the general US population. Usher syndrome is divided into three major types, I, II, and III. Type I is estimated to occur in about 1 in 25,000 newborns.

Genetics Home References: Usher syndrome (http://ghr.nlm.nih.gov/)

OMIM [USHER SYNDROME, TYPE I: 276900] (http://www.ncbi.nlm.nih.gov/omim)
Gene Reviews: Usher Syndrome Type I (http://www.ncbi.nlm.nih.gov/books/NBK1116/)

• Full gene sequencing